Limit switch



Sept. 9, 1947. LIB. WAGNER 2,427,317

mun syn-ca Filed Aug. 1, 1944' IN V EN TOR.

a? AQ/ Leland B. Wa er Patented Sept. 9, 19 47- Leland B. Wagner, Goshen, Indl, assignor to Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application August 1, 1944, Serial No. 547,607

My present invention relates to a switch structure particularly adaptable as a limit switch in a cowl flap control of the kind shown in the copending application of Ralph Penn, Serial No.

523,839, filed February 25, 1944.

One object of the invention is to provide a simple switch structure having a novel means for adjusting it in relation to an operating cam therefor so that the limit switch can operate for instance to shut off the current to a cowl flap operating motor, when the cowl flaps are completely or partially closed or open.

Another object is to arrange the adjusting. means in relation to the cam shaft so that there is no change in the operating relation of a cam and roller for operating the switch regardless of the position of adjustment.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my limit switch; whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, wherein: V

Figure 1 is a side elevation of a switch structure embodying my invention and showing it mounted on a main frame in which a cowl flap operating shaft is journalled and which carries a cam for operating the switch.

Figure 2 is an elevational view of Figure 1. Figures 3 and 4 are partial views of Figure 1 showing different positions of the structure of Figure 1, and

Figure 5 is a sectional view on the line 55 of Figure 2.

On the accompanying drawing I have used the reference numeral III to indicate a mainframe and I2 a secondary frame. The main frame I0 has a cowl operating shaft I4 journalled therein, which shaft may .have other purposes as the present invention is not limited to use in only the environment shown in the co-pending application abov mentioned. A cam lobe I6 is mounted on the shaft I4 as by being formed on a cam hub Ill. The hub in turn is pinned at I9 to the shaft.

The secondary frame I2 has a pair of ears I3 which are perforated as at I5. The ears are rotatable on the shaft I4 and the frame I2 is adapted to 'carry a switch comprising a leaf spring 20 having a movable contact 22 to cooperate with a stationary contact 24 carried by a somewhat stiffer spring 26. The springs 20 and 26 are provided with terminal lugs 28 and 36 for circuit connections and are secured to the secondary frame I2 as by screws 32 with suit- 2 Claims. (0]. 20047) able strips of insulation 34 interposed between them and the secondary frame. The stack of insulation strips embrace-a spring switch arm 36 and a stop arm 38. The switch arm 36 carries a roller 40 for operative cooperation with the cam I6 as will hereinafter appear.

The secondary frame I2 has a threaded boss 42 in which is threaded an adjusting screw 44 terminating in a ball head 46. The ball head 46 is seated in a socket 48 of the main frame I0 and retained in the socket by a cover plate 50 therefor. The socket 48, it will be noted by reference to Figures 1 and 5, is elongated in a plane radial to the axis of the shaft I4 so that as the secondary frame I2 is adjusted and the ball 46 thereby moves toward or away from the axis of rotation of the secondary frame, there will be no binding of the parts.

The spring arm 36 operates the contact arm 26 by means of a toggle spring 56 interposed between a finger 54 of the arm 36 and a finger 52 of the spring 26.

Practical operation In the operation of my limit switch, referring first to Figure 1, the roller 40 is being lifted by the cam I6. The toggle spring 52 is accordingly being swung from the position of Figure 4 toward the position of Figure 3 and passes over center just before the roller 40 is moved outwardly its maximumamount by the cam. The toggle spring then causes snap action of the leaf spring 20 from the position of Figure 1 to the Figure 3 position for breakingthe circuit.

When the cam I6 rotates in the opposite direction,'the roller 40 will move down the face of the cam as in Figure 1 and after the toggle spring causes snap action of the contacts to closed position, the roller will come to rest on the hub I6 of the cam during further movement of the cam.

The arrangement disclosed gives a relatively quick motion of the switch arm'36 during a small angle of movement of the cam and results in operation of the limit switch within a narrow differential so that it can be adjusted for openingthe cam shaft as an axis. Accordingly I am able to secure the desired adjustment in a micrometric manner so that the shaft M can be accurately stopped as by opening of the limit switch and consequent deenergization of the motor controlling the shaft. This is particularly important in cowl flap control for airplanes as it is desirable to have a limit switch which stops the cowl flaps at a predetermined open or closed position, depending upon the characteristics of the particular engine involved.

I have shown a limit switch for only one limit of movement whereas, as a general rule, there would be a second limit switch for the other limit of movement and even additional emergency limit switches for selective control by the pilot when a'quick get-away is necessary or a dog fight is imminent.

Some changes may be made in the construction and arrangement of the parts of my device with-.

out departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope without sacrificing any of the advantages thereof.

' I claim as my invention:

1. A switch structure comprising a main frame, a shaft journalled relative thereto, a secondary frame pivotally mounted for circumferential adjustment around said shaft, a switch carried by said secondary frame and including a switch arm,

a cam on said shaft for moving said switch arm, an adjusting screw rigidly carried by said secondary frame and having a ball head, said main frame having a socket to receive said head, said socket being elongated in a direction radial to said shaft and of substantially the same width as the diameter of said ball in a direction parallel to said shaft.

2. In a switch structure, a main frame, a shaft journalled relative thereto, a secondary frame pivotally mounted for circumferential adjustment around said shaft, 2. switch carried by said secondary frame and including a switch arm and a roller, a cam on said shaft for moving said roller away from said shaft for operating said switch, and an adjusting screw threaded in said secondary frame and having a ball and socket connection with said main frame which prevents axial movement of said adjustin screw relative to said main frame.

LELAND B. WAGNER.

REFERENCES CITED The following references are of record in the 

